Couple of minor notes on the code:
1) Detecting exists is best if you do the assignment using WaitAliasChild
Set updateAddWindow=mypage.WaitAliasChild('panelPnlupdate', 5000)
2) If you're actually expecting an array, you should use FindAllChildren instead of FindChild.
Now... that all said, if you want to click on a specific radio button, the For loop is not the way to do it, at least not as you have it. It will click on ALL the radio buttons.
So... what I would do.... I'm not sure how your developers set up your radio buttons but many times the radio button caption will be part of the component itself. So, I would do just a "FindChild" to look for the radio button but, instead of just looking for ObjectType alone, I'd add a second property in the find to look for the desired caption.
Dim PropArray, ValueArray
PropArray = Array("ObjectType", "Caption")
ValueArray = Array("RadioButton", "MyCaption")
Set objRadBtn = updateAddWindow.FindChild(PropArray, ValueArray, 20)
This will allow you to find the specific desired radio button. You can replace those property/value pairs with whatever you need to find the button you're looking for and then click on that button, no for-loop needed.